The present invention relates to an arrangement of parts for fastening a lens of a projector optical system of a headlamp, preferably for motor vehicles.
The headlamp projector system, used in motor vehicles instead of a conventional paraboloidal mirror, comprises of an ellipsoidal reflector, a lens, and in case of the dim and fog lamps, also of a screen placed in the lens focus. Said main parts have to be mutually adjusted accurately and stably so that there is no change in optical characteristics of the headlamp in operation caused by light source heat, vibrations or ageing of the used materials. Therefore, mainly metallic parts are used to fix the projector lens. Such parts are not subject of the above mentioned influences. For example, flexible wire rings are used. The rings are leaned against the oblique walls or lens holder depressions and they press the lens into an opening of this holder. Frames resembling a bayonet closure are also used. They hold the lens via a spring to the firm part of the holder. Such design methods of fixing the lens meet the requirements of thermal and mechanical stability but they are demanding with regard to high accuracy and low tolerances of parts. Another disadvantage is the fact that the lens holder requires to be provided with cutouts, which cutouts are used to fix the flexible parts. But some light radiates through such cutouts of the circumferential casing of the holder. To prevent this light loss it is necessary to use non-translucent masks covering the lens holder. However, such mask represents an additional headlamp part.
The above mentioned disadvantages are substantially removed in case of a lens holder according to this invention. The holder body of cylindrical or conical shape is connected with an ellipsoidal reflector and eventually with a screen. On the light output side, a lens is inserted in the holder so that its spherical part passes through an opening in the holder face. The lens border is pressed by springs inserted in the openings formed in the circumferential mantle in the plane of the internal surface of the lens. The springs are provided with an enlarged end, which end prevents that they can be taken out of the opening in the holder. The longer end of the spring, which spring is bent into an L-shape, is pressed to the circumferential mantle of the holder and in this position it is secured by bending the foot cut out on the holder body or on the spring, eventually it is inserted into an opening in the screen border or in the reflector which reflector is connected with the lens holder.
It is an advantage of this invention that a sufficient force presses the lens to rest in the holder also in case of substantial tolerances of the lens border. Overlapping of the openings by the springs passing through prevents that light passes outside the lens and allows to utilize the holder also as an appearance forming part of the headlamp without any necessity to use a covering mask.